Our laboratory has made the initial observations suggesting that endogenous opioid systems are related to nervous system development, and that perturbations of neuro-ontogeny (Science 221:1179-1180, 1983). During the past 8 years of this project the role of endogenous opioid systems in brain development has been carefully defined. We have identified [Met]-enkephalin, derived from preproenkephalin A (PPE), as the native peptide that serves as an opioid growth factor (OGF). OGF regulates the proliferation of both neuronal and glial precursors through inhibitory channels. The source of this peptide appears to be both autocrine (germinative cells) and paracrine (macronneurons). OGF interacts with the nuclear-associated zeta opioid receptor to regulate growth. The binding subunits have been identified and characterized, and polyclonal and monoclonal antibodies generated to these polypeptides. In this grant proposal, we continue to explore the thesis that an endogenous opioid system is important to neurrobiological development. The aims of this proposal are: (1) Determine the embryogenesis of OGF and PPE gene expression in the rat brain by immunocytochemistry, Northern analysis and in situ hybridization. (2) Define the ontogeny of the zeta receptor quantitatively (immunodot assay) and qualitatively (Western blotting and peptide mapping). (3) Ascertain the location of the zeta receptor by immunocytochemistry, immunoelectron microscopy, and in vitro autoradiography. (4) Isolate, purify, and characterize the native zeta receptor, and assess binding function by reconstitution experiments. (5) Clone and sequence the cDNA for the zeta receptor. (6) Examine the OGF and zeta receptor in developing human brain using immunocytochemistry, in vitro autoradiography, Western and ligand blotting, Northern analysis, and in situ hybridization. This research will contribute to comprehending the processes shaping normal brain development, and should be useful in understanding the etiology of developmentally-based neurobiological dysfunction. This research is part of a long-range program in cellular and molecular neurobiology which seeks to define the fundamental principles underlying normal and abnormal brain development.